This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The objective of this project is to find better and safer antiviral drugs to treat HIV infection. Simian immunodeficiency virus infection of newborn and infant macaques is a useful animal model of human AIDS to evaluate novel antiviral drugs. Previously, we initiated studies to evaluate the long-term therapeutic and toxic effects of tenofovir (9-[2-(phosphonomethoxy)-propyl]adenine;PMPA).